package com.example.web;

import java.awt.*;
import java.awt.image.*;
import java.io.IOException;
import java.util.Random;

import javax.servlet.*;
import javax.servlet.http.*;

import com.sun.image.codec.jpeg.*;

/**
 * @author JianpengTong
 * @since 2009-6-24
 * @version 1.0
 */
public class ValidationCodeServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 4341010031320206831L;
	HttpServletRequest request = null;
	HttpServletResponse response = null;
	HttpSession session = null;

	BufferedImage image = null;
	//  宽                            高                              干扰线数量           验证码长度         字体大小
	int width = 58, height = 18, grline = 155, length = 4, fontSize = 18;

	public void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doPost(req, resp);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.reset();
		response.setContentType("image/jpeg");
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);

		// 创建图像
		createImage();

		// 输出图象到页面
		ServletOutputStream out = response.getOutputStream();
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
		encoder.encode(image);
		out.close();
	}

	protected void createImage() {
		// 在内存中创建图象
		image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

		// 获取图形上下文
		Graphics g = image.getGraphics();

		// 生成随机数
		Random random = new Random();

		// 设定背景色
		g.setColor(new Color(201 + random.nextInt(50),
				201 + random.nextInt(50), 201 + random.nextInt(50)));

		g.fillRect(0, 0, width, height);

		// 设定字体
		g.setFont(new Font("Times new Roman", Font.PLAIN, fontSize));

		// 画边框
		// g.setColor(new Color());
		// g.drawRect(0,0,width-1,height-1);

		// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(new Color(160 + random.nextInt(41),
				160 + random.nextInt(41), 160 + random.nextInt(41)));

		for (int i = 0; i < grline; i++) {
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}

		// 取随机产生的认证码(4位数字)
		String sRand = "";

		for (int i = 0; i < length; i++) {
			String rand = String.valueOf(random.nextInt(10));
			sRand += rand;

			// 将认证码显示到图象中
			g.setColor(new Color(20 + random.nextInt(111), 20 + random
					.nextInt(111), 20 + random.nextInt(111)));

			// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
			g.drawString(rand, 13 * i + 6, 16);
		}
		session = request.getSession(true);
		// 将认证码存入SESSION
		session.setAttribute("rand", sRand);

		// 图象生效
		g.dispose();
	}
}
